The price a customer saw and the price the hotel is actually charging can be two different numbers — and the gap doesn't surface until check-in.
A booking error is any gap between what was promised at the time of booking and what the guest actually gets. Rate discrepancy is one of the quieter versions of it — a difference between the price advertised and the price a hotel is actually prepared to honour.
What that's looked like in practice
In one case, a hotel in Egypt rejected an international booking outright because the rate quoted wasn't the rate set for international guests — and asked for an extra $50 a night to honour the reservation at all. In another, a rate mismatch between the supplier and the hotel meant the booking never actually got confirmed on the hotel's side, and needed both parties to sort it out before the guest could check in.
Either way, the guest finds out at the desk — the worst place to discover an unexpected charge or a booking that isn't actually held. Catching a rate mismatch before that point is what re-verification is for: confirming, directly with the property, that the price on the confirmation is still the price at the desk.
